A Four-Wheel Drive Vehicle Torque Vectoring and Shift Control Method and System

Abstract

The present invention discloses a torque vectoring and shifting control method and system for a four-wheel drive vehicle, comprising the steps of: determining the torque demand of the current vehicle; collecting the front wheel steering angle and yaw rate of the current vehicle; judging whether the current vehicle is in a turning state according to the collected front wheel steering angle and yaw rate; when it is judged that the vehicle is not in a turning state, adjusting the optimal distributed torque of the front axle driver and the rear axle driver according to the principle of the best overall vehicle comprehensive efficiency, and at the same time determining the optimal gear of the rear axle driver; when it is judged that the vehicle is in a turning state, adjusting the optimal distributed torque of the front axle driver and the rear axle driver according to the principle of the best vehicle attitude stability; which solves the problems that the torque control of the existing dual-power four-wheel drive vehicle cannot fit the actual driving state, has high energy consumption and poor driving stability, improves the accuracy of the torque control strategy, and gives full play to the power performance of the vehicle.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle torque control, and particularly to a torque vectoring and shifting control method and system for a four-wheel drive vehicle. Background Art

[0002] Currently, with new energy vehicles attracting more and more attention from the industry, countries, and even the world, how to control new energy vehicles more perfectly is an important issue that needs to be considered at present. Compared with traditional fuel vehicles, the power form and transmission method of new energy vehicles have undergone huge changes. Currently, some hybrid vehicles adopt a dual-power source distributed drive method, that is, a driver such as a motor or an engine drives the front axle through a transmission, while a driver such as a motor drives the rear axle alone, and there is no mechanical connection between the front and rear axles; or some four-wheel drive pure electric vehicles use one motor arranged on each of the front and rear axles for driving. Since there is no mechanical connection between the front and rear axles, a torque distribution strategy needs to be set in the above-mentioned vehicles to ensure the torque distribution of the front and rear axles based on the vehicle state and road conditions, so as to ensure the stable operation of the overall vehicle and reduce energy consumption.

[0003] However, during the actual use of the above-mentioned vehicles, due to the randomness of the vehicle state and road surface state, the load on the front and rear axles of the vehicle will change randomly during actual operation. However, the above-mentioned random changes are not considered in the current torque distribution strategy, which will lead to the torque distribution strategy not being able to accurately fit the actual state of the vehicle, unable to better exert the power performance of the vehicle, and even seriously may lead to the vehicle being unable to be stably controlled, causing driving hazards. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a torque vectoring and shifting control method and system for a four-wheel drive vehicle, which solves the problems that the torque control of existing dual-power four-wheel drive vehicles cannot fit the actual driving state, has high energy consumption and poor driving stability, thereby overcoming the deficiencies of the prior art.

[0005] To solve the above technical problem, the present invention provides a torque vectoring and shifting control method for a four-wheel drive vehicle, which includes the following steps:

[0006] Determine the torque requirement of the current vehicle;

[0007] Collect the front wheel angle and yaw angular velocity of the current vehicle;

[0008] Judge whether the current vehicle is in a turning state according to the collected front wheel angle and yaw angular velocity;

[0009] When it is determined that the vehicle is not in a turning state, according to the principle of the best overall vehicle efficiency, the optimal distribution torque of the front axle drive and the rear axle drive is adjusted, and at the same time, the optimal gear of the rear axle drive is determined; when it is determined that the vehicle is in a turning state, according to the principle of the best vehicle attitude stability, the optimal distribution torque of the front axle drive and the rear axle drive is adjusted;

[0010] When a gear shift is required, according to the requirements of the selected optimal gear, it is judged whether to enter the corresponding gear shift control process.

[0011] As an improvement of the present invention, the specific steps of adjusting the optimal distribution torque of the front axle drive and the rear axle drive according to the principle of the best overall vehicle efficiency in the non-turning state of the vehicle are as follows:

[0012] First, based on the power-torque relationship of the front axle drive and the relationship between the vehicle's required speed and the rotational speed of the front axle drive, the relationship between the power of the front axle drive and the vehicle's required speed is obtained;

[0013] Based on the power-torque relationship of the rear axle drive and the relationship between the vehicle's required speed and the torque of the rear axle drive, the relationship between the power of the rear axle drive and the vehicle's required speed is obtained;

[0014] Based on the balance relationship, torque sum relationship of the driving force, rolling resistance, air resistance, ramp resistance and acceleration resistance of the current vehicle, and combined with the motor loss efficiency curve, the optimal distribution torque of the front axle drive and the rear axle drive is obtained, and the current corresponding optimal gear of the rear axle drive is determined.

[0015] As a further improvement of the present invention, the specific method for obtaining the relationship between the power of the front axle drive and the vehicle's required speed is as follows:

[0016] First, according to the power-torque relationship of the front axle drive:

[0017]

[0018] where P A is the power of the front axle drive or the engine; n A is the output rotational speed of the front axle drive; T A is the torque of the front axle drive or the engine;

[0019] and the relationship between the vehicle's required speed and the rotational speed of the front axle drive:

[0020]

[0021] where i A is the gear ratio of the front axle drive; n A is the output rotational speed of the front axle drive; V is the vehicle speed; R is the wheel radius;

[0022] The relationship between the power of the front axle drive and the vehicle demand speed obtained by calculation is as follows:

[0023]

[0024] As an improvement of the present invention, the specific method for obtaining the relationship between the power of the rear axle drive and the vehicle demand speed is as follows:

[0025] First, according to the relationship between the power and torque of the rear axle drive:

[0026]

[0027] where P B is the power of the rear axle drive; n B is the output speed of the rear axle drive; T B is the torque of the rear axle drive;

[0028] and the relationship between the vehicle demand speed and the torque of the rear axle drive:

[0029]

[0030] where i B is the gear ratio of the rear axle drive, n B is the output speed of the rear axle drive; V is the vehicle speed; R is the wheel radius;

[0031] The relationship between the power of the rear axle drive and the vehicle demand speed obtained by calculation is as follows:

[0032]

[0033] As a further improvement of the present invention, the specific method for obtaining the optimal distribution torque of the front axle drive and the rear axle drive is as follows:

[0034] First, according to the balance relationship of the driving force, rolling resistance, air resistance, ramp resistance and acceleration resistance of the current vehicle:

[0035]

[0036] where P is the vehicle power, V is the vehicle speed, η t is the equivalent efficiency of the vehicle transmission system, m is the vehicle mass, f is the vehicle rolling friction coefficient, α is the vehicle ramp angle, C D is the air resistance coefficient, A is the vehicle frontal area, δ is the vehicle acceleration resistance coefficient, is the vehicle acceleration, P A is the power of the front axle drive, P B is the power of the rear axle drive;

[0037] and the relationship of the total vehicle torque,

[0038] T = T A + T B ,

[0039] where T is the torque of the whole vehicle, T A is the torque of the front axle driver, and T B is the torque of the rear axle driver;

[0040] And combine the loss equation of the loss efficiency curves of the front axle driver and the rear axle driver:

[0041]

[0042] where is the efficiency percentage of the front axle driver at different torques, is the efficiency percentage of the rear axle driver at different torques, is the efficiency of the front axle driver at different torques, is the efficiency of the rear axle driver at different torques;

[0043] Finally, the optimal distribution torques T A and T B of the front axle driver and the rear axle driver are obtained.

[0044] As an improvement of the present invention, the specific steps for adjusting the optimal distribution torques of the front axle driver and the rear axle driver according to the principle of optimal vehicle attitude stability in the vehicle turning state are as follows:

[0045] Use the trained bicycle model to predict the yaw rate of the four-wheel drive vehicle;

[0046] According to the predicted yaw rate of the four-wheel drive vehicle and in combination with the bicycle model, judge the vehicle turning state;

[0047] According to the judged vehicle turning state: whether it is oversteering or understeering, actively distribute the torques of the front axle driver and the rear axle driver.

[0048] As an improvement of the present invention, the specific method for the vehicle to judge whether to enter the corresponding shift control process is as follows:

[0049] First, determine the corresponding optimal gear ratio according to the final torque distributed to the rear axle driver, and determine the optimal target gear according to the optimal gear ratio.

[0050] Combined with the current shift fork position, judge whether to execute the shift control process: if it is judged that the current shift fork position is at the optimal target gear, do not execute the shift control process; if it is judged that the current shift fork position is not at the optimal target gear, then execute the shift control process, and the shift control process includes a gear disengagement control stage, a free travel stage, and a gear engagement control stage.

[0051] As a further improvement of the present invention, the specific operation process of the gear disengaging control stage is as follows:

[0052] First, the determined target gear sets a preset torque value for the rear axle drive to perform the gear disengaging operation;

[0053] Compare the current torque of the rear axle drive with the preset torque value. If the current torque of the rear axle drive is less than or equal to the preset torque value, the shift actuator of the rear axle is activated, and the shift execution mechanism is controlled to perform the gear disengaging action; if the current torque of the rear axle drive is greater than the preset torque value, communicate with the vehicle controller to make the rear axle drive continue to perform the torque unloading action until the torque of the rear axle drive is less than or equal to the preset torque value.

[0054] As a further improvement of the present invention, the specific operation process of the gear engaging control stage is as follows:

[0055] First, a target difference range between the actual speed of the motor and the speed of the engaging teeth in the target gear is preset when the gear engaging operation is allowed to be performed.

[0056] After the gear disengaging action is completed, first control the speed of the rear axle drive so that the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear is within the target difference range, and then perform the gear engaging operation;

[0057] If the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear is not within the target difference range, continue to control the rear axle drive until the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear meets the target difference range.

[0058] In addition, the present invention discloses a four-wheel drive vehicle torque vectoring and shift control system. The four-wheel drive vehicle includes a front axle and a rear axle. The front axle uses a single-gear three-in-one electric drive system or a PX architecture hybrid system for power control, and the rear axle uses a two-gear three-in-one electric drive system for power drive. Among them, this system uses the above-mentioned four-wheel drive vehicle torque vectoring and shift control method to control the vehicle torque.

[0059] After adopting such a design, the present invention has at least the following advantages:

[0060] (1) The four-wheel drive vehicle torque vectoring and shift control system of the present invention includes two parts: a front axle and a rear axle. The front axle includes a single-gear three-in-one electric drive system or a PX architecture hybrid system, and the rear axle includes a two-gear three-in-one electric drive system. The two power systems of the front and rear axles can drive the vehicle independently to achieve the two-wheel drive function, or torque coupling can be performed to jointly drive the vehicle to achieve the four-wheel drive function, so that the vehicle can realize the timely switching between two-wheel drive and four-wheel drive to ensure stable vehicle passage.

[0061] (2) The torque vectoring and shifting control method for four-wheel drive vehicles in the present invention fully combines the current vehicle condition and road condition. When the vehicle is moving straight, based on the principle of optimal overall vehicle efficiency, torque vectoring control is performed on the front axle and the rear axle, so that the vehicle runs in the optimal working mode. At the same time, the rear axle gear shifts according to the result of the overall vehicle torque vectoring control, so that the rear axle drive works under the best efficiency condition, so that both the front axle drive and the rear axle drive operate efficiently at the best working efficiency point. It ensures that the acceleration performance and climbing performance of the vehicle remain unchanged, and at the same time, it can reduce the power consumption or fuel consumption. When the vehicle is cornering, the overall vehicle torque vectoring control is performed based on the principle of optimal vehicle attitude stability to avoid oversteering or understeering of the vehicle, thereby improving the overall vehicle body stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The above is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, the following further describes the present invention in detail in conjunction with the drawings and specific embodiments.

[0063] Figure 1 It is a schematic structural diagram of a torque vectoring and shifting control system for a four-wheel drive vehicle in Embodiment 2 of the present invention.

[0064] Figure 2 It is a schematic structural diagram of the drive system in the rear axle in Embodiment 2 of the present invention.

[0065] Figure 3 It is a schematic flowchart of a torque vectoring and shifting control method for a four-wheel drive vehicle in Embodiment 1 of the present invention.

[0066] Figure 4 It is a schematic operation diagram of the gear disengaging control stage in Embodiment 1 of the present invention.

[0067] Figure 5 It is a schematic operation diagram of the gear engaging control stage in Embodiment 1 of the present invention.

[0068] Figure 6 It is a schematic diagram of the position of the shift fork controlling the sliding sleeve displacement at different gears in the shift system of Embodiment 2 of the present invention.

[0069] Figure 7 It is a schematic diagram of the stroke of the shift system for shifting gears in Embodiment 2 of the present invention.

[0070] The meanings of the reference numerals in the drawings:

[0071] 1-First-gear first-stage driving gear; 2-First-gear dog clutch gear; 3-Shifting fork; 4-Sliding sleeve; 5-Sliding sleeve guide rail; 6-Second-gear first-stage driving gear; 7-Second-gear dog clutch gear; 8-Input shaft; 9-Second-gear first-stage driven gear; 10-First-gear first-stage driven gear; 11-Intermediate shaft; 12-Second-stage driving gear; 13-Second-stage driven gear; 14-Differential; 15-Left half shaft; 16-Right half shaft. Detailed implementation mode

[0072] Examples of the embodiments in the present invention are shown in the drawings, where the same or similar reference numerals denote the same or similar components or components with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0073] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the connection inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0074] Embodiment 1:

[0075] Combined with Figure 3 As shown, in this embodiment 1, the present invention specifically discloses a four-wheel drive vehicle torque vectoring and shifting control method, which includes the following steps:

[0076] Determine the torque demand of the current vehicle;

[0077] Collect the front wheel angle and yaw rate of the current vehicle;

[0078] According to the collected front wheel angle and yaw rate, determine whether the current vehicle is in a turning state;

[0079] When it is determined that the vehicle is not in a turning state, according to the principle of the best overall vehicle efficiency, adjust the best distributed torque of the front axle drive and the rear axle drive, and at the same time determine the best gear of the rear axle drive; when it is determined that the vehicle is in a turning state, according to the principle of the best vehicle attitude stability, adjust the best distributed torque of the front axle drive and the rear axle drive;

[0080] When shifting is required, according to the demand of the selected best gear, determine whether to enter the corresponding shifting control process.

[0081] Specifically, in this Embodiment 1, the specific steps for adjusting the optimal distribution torque of the front axle drive and the rear axle drive according to the principle of the best overall vehicle efficiency in the non-turning state of the vehicle are as follows:

[0082] Step 1: Based on the power-torque relationship of the front axle drive and the relationship between the vehicle's required speed and the rotational speed of the front axle drive, obtain the relationship between the power of the front axle drive and the vehicle's required speed;

[0083] First, according to the power-torque relationship of the front axle drive:

[0084]

[0085] where P A is the power of the front axle drive or the engine; n A is the output rotational speed of the front axle drive; T A is the torque of the front axle drive or the engine;

[0086] and the relationship between the vehicle's required speed and the rotational speed of the front axle drive:

[0087]

[0088] where i A is the gear ratio of the front axle drive; n A is the output rotational speed of the front axle drive; V is the vehicle speed; R is the wheel radius;

[0089] Calculate to obtain the relationship between the power of the front axle drive and the vehicle's required speed as:

[0090]

[0091] Step 2: Based on the power-torque relationship of the rear axle drive and the relationship between the vehicle's required speed and the torque of the rear axle drive, obtain the relationship between the power of the rear axle drive and the vehicle's required speed;

[0092] Similarly, first according to the power-torque relationship of the rear axle drive:

[0093]

[0094] where P B is the power of the rear axle drive; n B is the output rotational speed of the rear axle drive; T B is the torque of the rear axle drive;

[0095] and the relationship between the vehicle's required speed and the torque of the rear axle drive:

[0096]

[0097] where iB The gear ratio of the rear axle drive is n B The output speed of the rear axle drive; V is the vehicle speed; R is the wheel radius;

[0098] The relationship between the power of the rear axle drive and the vehicle demand speed obtained by calculation is:

[0099]

[0100] Step 3: Based on the balance relationship, torque sum relationship of the driving force, rolling resistance, air resistance, ramp resistance and acceleration resistance of the current vehicle, and combined with the motor loss efficiency curve, obtain the optimal distribution torque sum of the front axle drive and the rear axle drive, and determine the current optimal gear of the rear axle drive.

[0101] Specifically, first, based on the balance relationship of the driving force, rolling resistance, air resistance, ramp resistance and acceleration resistance of the current vehicle:

[0102]

[0103] where P is the vehicle power, V is the vehicle speed, η t is the equivalent efficiency of the vehicle transmission system, m is the vehicle mass, f is the vehicle rolling friction coefficient, α is the vehicle ramp angle, C D is the air resistance coefficient, A is the vehicle frontal area, δ is the vehicle acceleration resistance coefficient, is the vehicle acceleration, P A is the power of the front axle drive, P B is the power of the rear axle drive;

[0104] and the vehicle torque sum relationship,

[0105] T = T A + T B ,

[0106] where T is the vehicle torque, T A is the torque of the front axle drive, T B is the torque of the rear axle drive;

[0107] and combined with the loss equation of the loss efficiency curves of the front axle drive and the rear axle drive:

[0108]

[0109] where is the efficiency percentage of the front axle drive at different torques, is the efficiency percentage of the rear axle drive at different torques, is the efficiency of the front axle drive at different torques, is the efficiency of the rear axle drive at different torques;

[0110] Finally, the optimal distribution torques T A and T B .

[0111] It should be noted that the units of the above parameters all adopt the international unit standard.

[0112] Furthermore, in this Embodiment 1, the specific steps for adjusting the optimal distribution torques of the front axle drive and the rear axle drive according to the principle of the best vehicle body attitude stability during the vehicle turning state are as follows:

[0113] Step 1: Use the trained bicycle model to predict the yaw rate of the four-wheel drive vehicle;

[0114] Step 2: According to the predicted yaw rate of the four-wheel drive vehicle, combined with the bicycle model, judge the vehicle turning state;

[0115] Step 3: According to the vehicle turning state, oversteering or understeering, actively distribute the torque sum of the front axle and the rear axle.

[0116] It should be noted that the process of adjusting the optimal distribution torques of the front axle drive and the rear axle drive according to the principle of the best vehicle body attitude stability in this embodiment is the prior art. For example, the technical content contained in the Chinese patent document

Patent No.: CN202010605931

[0117] More specifically, in this Embodiment 1, when the vehicle needs to shift gears, it will judge whether to enter the corresponding shift control process according to the required optimal gear position. The specific method is as follows:

[0118] First, determine the corresponding optimal gear ratio according to the optimal torque distributed by the rear axle drive, and determine the optimal target gear position according to the optimal gear ratio.

[0119] Combined with the current shift fork position, judge whether to execute the shift control process: If it is judged that the current shift fork position is at the optimal target gear position, do not execute the shift control process; if it is judged that the current shift fork position is not at the optimal target gear position, then execute the shift control process, and the shift control process includes a gear disengagement control stage, a free travel stage, and a gear engagement control stage.

[0120] Specifically, as Figure 4 shown, the specific operation process of the gear disengagement control stage in this Embodiment 1 is as follows:

[0121] Step 1: First, determine the preset torque value for the rear axle drive to perform the gear disengagement operation for the target gear position set.

[0122] Step 2: Compare the current torque of the rear axle drive with the preset torque value. If the current torque of the rear axle drive is less than or equal to the preset torque value, the shift actuator of the rear axle is activated, and the shift execution mechanism is controlled to perform the gear disengagement action. If the current torque of the rear axle drive is greater than the preset torque value, communicate with the vehicle controller to make the rear axle drive continue to perform the torque unloading operation until the torque of the rear axle drive is less than or equal to the preset torque value. Through the above gear disengagement process, it is possible to avoid difficulties in gear disengagement or stall phenomena during the gear shift of the rear axle drive, etc., to ensure smooth gear shifting.

[0123] More specifically, as Figure 5 shown, the specific operation process in the gear engagement control stage in Embodiment 1 is as follows:

[0124] Step 1: First, preset the target difference range between the actual speed of the motor and the speed of the engaging teeth in the target gear position when allowing the gear engagement operation.

[0125] Step 2: After the gear disengagement action is completed, first control the speed of the rear axle drive so that the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear position is within the target difference range, and then perform the gear engagement operation.

[0126] Step 3: If the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear position is not within the target difference range, continue to control the rear axle drive until the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear position meets the target difference range. According to the above gear engagement process, it can ensure the smooth transmission between the rear axle drive and the engaging teeth of the target gear during the gear change, and ensure the stability of the driving process.

[0127] Embodiment 2:

[0128] In addition, in this Embodiment 2, a four-wheel drive vehicle torque vectoring and shift control system is disclosed. As Figure 1 and Figure 2 shown, the four-wheel drive vehicle includes a front axle and a rear axle. The front axle uses a single-speed three-in-one electric drive system or a PX architecture hybrid system for power control, and the rear axle uses a two-speed three-in-one electric drive system for power drive. This system uses the four-wheel drive vehicle torque vectoring and shift control method described in Embodiment 1 for vehicle torque control.

[0129] Specifically, the two-speed integrated electric drive system in this Embodiment 2 includes a drive motor, a shifting system, an input shaft 8, an intermediate shaft 11, and a differential 14. The drive motor provides a power source for the power system of the rear axle. The power of the drive motor is transmitted to the differential 14 through the input shaft 8 and the intermediate shaft 11, and the differential 14 distributes the power to the rear wheels connected to both sides of the differential 14. The shifting system is used to control the input power of the drive motor and change the transmission ratio.

[0130] The shifting system includes a shifting motor, a shifting fork 3, a sliding sleeve 4, a sliding sleeve guide rail 5, a first-gear first-stage driving gear 1, a first-gear dog clutch gear 2, a second-gear first-stage driving gear 6, and a second-gear dog clutch gear 7. The first-gear first-stage driving gear 1 and the second-gear first-stage driving gear 6 are respectively fixed to the input shaft 8, and the first-gear dog clutch gear 2 is fixed to the first-gear first-stage driving gear 1, and the second-gear dog clutch gear 7 is fixed to the second-gear first-stage driving gear 6. The sliding sleeve guide rail 5 is fixed to the input shaft 8 between the first-gear first-stage driving gear 1 and the second-gear first-stage driving gear 6. The sliding sleeve 4 is sleeved on the sliding sleeve guide rail 5. One end of the shifting fork 3 is connected to the sliding sleeve 4, and the other end is connected to the output shaft of the shifting motor. The shifting motor drives the shifting fork 3 to horizontally move the sliding sleeve 4 axially along the sliding sleeve guide rail 5, and the sliding sleeve 4 and the sliding sleeve guide rail 5 rotate synchronously in the circumferential direction. In the above structure, the shifting motor drives the shifting fork 3 to switch the sliding sleeve 4 to move left or right, so that the gear arranged at the end face position of the sliding sleeve 4 meshes with the first-gear dog clutch gear 2 or the second-gear dog clutch gear 7, so as to transmit the power of the drive motor to the corresponding gear on the intermediate shaft 11 through the first-gear first-stage driving gear 1 or the second-gear first-stage driving gear 6. Since the number of teeth of the first-gear first-stage driving gear 1 or the second-gear first-stage driving gear 6 is different, the transmission ratio of the power can be changed, and finally the rear wheels rotate at different speeds.

[0131] Further, a first-gear first-stage driven gear 10, a second-gear first-stage driven gear 9, and a second-stage driving gear 12 are provided on the intermediate shaft 11. The first-gear first-stage driven gear 10 and the second-gear first-stage driven gear 9 are respectively fixedly connected to the intermediate shaft 11. The first-gear first-stage driven gear 10 is meshed and connected with the first-gear first-stage driving gear 1, and the second-gear first-stage driven gear 9 is meshed and connected with the second-gear first-stage driving gear 6. The second-stage driving gear 12 is fixedly connected to the intermediate shaft 11, and the second-stage driving gear 12 is meshed and connected with a second-stage driven gear 13. The second-stage driven gear 13 is fixedly connected to the differential 14. When the shifting fork 3 is switched so that the gear arranged at the end face position of the sliding sleeve 4 meshes with the first-gear dog clutch gear 2 or the second-gear dog clutch gear 7 respectively, due to the different transmission ratios of the first-gear first-stage gear set and the second-gear first-stage gear set, the rotation speed of the intermediate shaft 11 is changed, and then through the second-stage gear set of the intermediate shaft 11, the power is transmitted to the differential 14 at different rotation speeds, and the differential 14 distributes the power to the rear wheels.

[0132] Combined with Figure 6 As shown, when the shift fork 3 is in the leftmost position, i.e., the P1 position, it is the second gear shift fork position. When the shift fork 3 is in the rightmost position, i.e., the P3 position, it is the first gear shift fork position. When the shift fork 3 is in the middle position, i.e., the P2 position, it is the neutral gear shift fork position. Combined with Figure 7 As shown, when the shift fork 3 switches from the first gear to the second gear, the displacement stroke of the shift fork 3 is the shift stroke L; when shifting out of gear, when the shift fork 3 moves from the end limit position to the position where the sliding sleeve 4 is completely disengaged from the dog tooth engaging teeth, its displacement stroke is the out-of-gear stroke L1; and the displacement stroke of the shift fork 3 from the completion of the out-of-gear operation until the sliding sleeve 4 starts to engage with another dog tooth engaging tooth is the free stroke of the shift fork 3, where the free stroke is greater than the out-of-gear stroke L1 and at the same time the free stroke is less than the difference between the spacing L2 of the dog tooth engaging teeth between the two gears and the length L3 of the sliding sleeve 4.

[0133] The above are only the preferred embodiments of the present invention and do not impose any formal limitations on the present invention. Any simple modifications, equivalent changes or decorations made by those skilled in the art using the disclosed technical content all fall within the protection scope of the present invention.

Claims

1. A four-wheel drive vehicle torque vectoring and shift control method, characterized in that, It includes the following steps: Determine the torque demand of the current vehicle; Collect the front wheel steering angle and yaw rate of the current vehicle; Judge whether the current vehicle is in a turning state according to the collected front wheel steering angle and yaw rate; When it is judged that the vehicle is not in a turning state, adjust the optimal distributed torques Ta and Tb of the front axle drive and the rear axle drive according to the principle of the best overall vehicle comprehensive efficiency, and at the same time determine the optimal gear of the rear axle drive; when it is judged that the vehicle is in a turning state, adjust the optimal distributed torques Ta and Tb of the front axle drive and the rear axle drive according to the principle of the best overall vehicle attitude stability, and reduce understeer or oversteer; When a gear shift is required, judge whether to enter the corresponding gear shift control process according to the required optimal gear; The specific steps for adjusting the optimal distributed torques of the front axle drive and the rear axle drive according to the principle of the best overall vehicle comprehensive efficiency in the non-turning state of the vehicle are as follows: First, based on the power-torque relationship of the front axle drive and the relationship between the required vehicle speed of the whole vehicle and the rotational speed of the front axle drive, obtain the relationship between the power of the front axle drive and the required vehicle speed of the whole vehicle; Based on the power-torque relationship of the rear axle drive and the relationship between the required vehicle speed of the whole vehicle and the torque of the rear axle drive, obtain the relationship between the power of the rear axle drive and the required vehicle speed of the whole vehicle; Based on the balance relationship, torque sum relationship of the driving force, rolling resistance, air resistance, slope resistance and acceleration resistance of the current vehicle, and combined with the drive loss efficiency curve, obtain the optimal distributed torques of the front axle drive and the rear axle drive, and determine the current corresponding optimal gear of the rear axle drive.

2. The four-wheel drive vehicle torque vectoring and shift control method according to claim 1, wherein The specific method for obtaining the relationship between the power of the front axle drive and the required vehicle speed of the whole vehicle is as follows: First, according to the power-torque relationship of the front axle drive: Among them, P A is the front axle driver or engine power; n A is the output speed of the front axle driver; T A is the torque of the front axle driver or engine; And the relationship between the required vehicle speed of the whole vehicle and the rotational speed of the front axle drive: where i A is the gear ratio of the front axle drive; n A is the output speed of the front axle drive; V is the vehicle speed; R is the wheel radius; Calculate to obtain the relationship between the power of the front axle drive and the required vehicle speed of the whole vehicle as:

3. The four-wheel drive vehicle torque vectoring and shift control method according to claim 1, characterized in that The specific method for obtaining the relationship between the power of the rear axle drive and the required vehicle speed of the whole vehicle is as follows: First, according to the power-torque relationship of the rear axle drive: Among them, P B is the power of the rear axle driver; n B is the output speed of the rear axle driver; T B is the torque of the rear axle driver; And the relationship between the required vehicle speed of the whole vehicle and the torque of the rear axle drive: where i B is the gear ratio of the rear axle drive, n B is the output speed of the rear axle drive; V is the vehicle speed; R is the wheel radius; Calculate to obtain the relationship between the power of the rear axle drive and the required vehicle speed of the whole vehicle as:

4. The torque vectoring and shift control method for a four-wheel drive vehicle according to claim 1, wherein The specific method for obtaining the optimal distributed torques of the front axle drive and the rear axle drive is as follows: First, according to the balance relationship formula of the driving force, rolling resistance, air resistance, slope resistance and acceleration resistance of the current vehicle: Among them, P is the vehicle power, V is the vehicle speed, η t is the equivalent efficiency of the vehicle transmission system, m is the vehicle mass, f is the vehicle rolling friction coefficient, α is the vehicle ramp angle, C D is the air resistance coefficient, A is the vehicle frontal area, δ is the vehicle acceleration resistance coefficient, is the vehicle acceleration, P A is the power of the front axle driver, P B is the power of the rear axle driver; And the whole vehicle torque sum relationship formula, T = T A + T B Among them, T is the torque of the whole vehicle, T A is the torque of the front axle driver, T B is the torque of the rear axle driver; And combined with the loss equation of the front axle and rear axle drive loss efficiency curve: wherein is the efficiency percentage of the front axle drive at different torques, is the efficiency percentage of the rear axle drive at different torques, is the efficiency of the front axle drive at different torques, is the efficiency of the rear axle drive at different torques; By simultaneously solving the balance relation formula, the total vehicle torque relation formula, and the loss equation, the optimal distributed torques T A and T B are finally obtained.

5. The torque vectoring and shift control method for a four-wheel drive vehicle according to claim 1, wherein The specific steps for adjusting the optimal distributed torques of the front axle drive and the rear axle drive according to the principle of the best overall vehicle attitude stability in the turning state of the vehicle are as follows: Use the trained bicycle model to predict the yaw rate of the four-wheel drive vehicle; According to the predicted yaw rate of the four-wheel drive vehicle, combined with the bicycle model, judge the turning state of the vehicle; According to the judged turning state of the vehicle, oversteer or understeer, actively distribute the torques of the front axle and the rear axle.

6. The torque vectoring and shift control method for a four-wheel drive vehicle according to claim 1, wherein The specific method for the vehicle to judge whether to enter the corresponding gear shift control process is as follows: First, determine the corresponding optimal gear ratio according to the optimal torque distributed to the rear axle drive, and determine the optimal target gear according to the optimal gear ratio, Based on the current shift fork position, determine whether to execute the shift control process: If it is determined that the current shift fork position is at the optimal target gear, do not execute the shift control process; If it is determined that the current shift fork position is not at the optimal target gear, then execute the shift control process, which includes a gear disengagement control stage, a free travel stage, and a gear engagement control stage.

7. The four-wheel drive vehicle torque vectoring and shift control method according to claim 6, characterized in that, The specific operation process of the gear disengagement control stage is as follows: First, set the preset torque value for the rear axle drive to perform the gear disengagement operation according to the determined target gear; Compare the current torque of the rear axle drive with the preset torque value. If the current torque of the rear axle drive is less than or equal to the preset torque value, the shift actuator of the rear axle starts and controls the shift execution mechanism to perform the gear disengagement action; if the current torque of the rear axle drive is greater than the preset torque value, communicate with the vehicle controller to make the rear axle drive continue to perform the torque unloading action until the torque of the rear axle drive is less than or equal to the preset torque value.

8. The four-wheel drive vehicle torque vectoring and shift control method according to claim 6, characterized in that The specific operation process of the gear engagement control stage is as follows: First, preset the target difference range between the actual speed of the drive and the speed of the engaging teeth in the target gear when the gear engagement operation is allowed to be executed, After the gear disengagement action is completed, first control the speed of the rear axle drive so that the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear is within the target difference range, and then execute the gear engagement operation; If the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear is not within the target difference range, continue to control the rear axle drive until the difference between the actual speed of the rear axle drive and the speed of the engaging teeth in the target gear meets the target difference range.

9. A four-wheel drive vehicle torque vectoring and shift control system, the four-wheel drive vehicle including a front axle and a rear axle, the front axle using a single-gear three-in-one electric drive system or a PX architecture hybrid system for power control, and the rear axle using a two-gear three-in-one electric drive system for power drive, characterized in that, This system uses the four-wheel drive vehicle torque vectoring and shift control method described in any one of claims 1-8 to control the vehicle torque.

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